This study is quantitatively characterizing various structural abnormalities in the lungs of coal workers and controls. Structural abnormalities are then correlated with X-ray findings, antemortem medical and occupational histories. Since it deals with postmortem material, it is retrospective. Prospective studies will determine if mechanisms of cell based immunity play any role in coal workers' pneumoconiosis. A variety of antigens are being used in the in-vitro tests, antigens that have been identified in the underground, mining environment.